drm/imx: ldb: drop custom EDID support

drm/imx: ldb: drop custom EDID support

Bindings for the imx-ldb never allowed specifying the EDID in DT. None
of the existing DT files use it. Drop it now in favour of using debugfs
overrides or the drm.edid_firmware support.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # on imx6q-nitrogen6x
Link: https://patchwork.freedesktop.org/patch/msgid/20240602-drm-imx-cleanup-v3-5-e549e2a43100@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>